Mistress9 is the main villain in Sailor Moon S ( third seasone ). She doesn't have her own body, but lives in Hotaru's as her second personality. To get her alive her minors had to give her Chibi Usa's pure hart. After eating it Hotaru transformed into Mistress9. In the moment she woke up, she killed Kaorinite ( who actually brought her this hart ), saying she was no longer needed.
Her goal was to bring Pharoah90 to Earth.

Mistress9 gethers Holy Grale by asking dr. Tomoe to beg Sailor Moon for it. She transformes the Grale into energy needed for Pharoah90 to get to Earth. After that Mugen school transformes into an energy ball and destroyes the city. But Sailor Moon heales Mistress9 and Hotaru fights against the incoming evil.